Renewable fuse



R. C. COLE.

RENEWABLE FUSE.

APPLICATION FILED SEPT. 3, 1919.

Patented Dec. 20, 1921.

- UNITED sures ROBERT C. COLE, OF HARTFORD, CONNECTICUT, ASSIGNOB TO THEJOHNS- COIPLNY, O1 HARTFORD,

PATENT OFFICE.

PRATT CONNECTICUT, A CORPORATION OF CONNECTICUT.

RENEWABLE FUSE.

Specification of Letters Patent.

Patented Dec. 20, 1921.

To all whom it may concern:

Be it known that I, ROBERT C. C OLE, a citizen of the United States,residing at Hartford, in the county of Hartford and State ofConnecticut, have invented a new and useful Improvement in Renewable"Fuses, of which the following is a specification.

terminal.

This invention relates to the construction of inclosed electric fuseswhich are commonl known as renewable cartridge fuses, that is, thosefuses which, when the fusible link is melted, can be quickly taken apartand a new link substituted, and particularly to the type of knife-bladecontact fuses of this class.

The object of the invention is to so construct a fuse of the charactermentioned that it may be cheaply manufactured, uickly assembled forservice and easily ta en apart for renewal, and will have sufficientmechanical strength to sustain an internal pressure which can resultfrom e conver sion of the metal of the fusible link from a solid to agaseous condition with the incident liberation of heat and burning ofthe arc due to excess or abnormal current flow, without the emission ofany flash 0r flame.

Figure 1 of the accompanying draw ngs is a view of a fuse which embodiesthe invention with the casing and ferrules cut in central section toshow the interior construction. Fig. 2 is a view looking toward-one endwith the ferrule washers and cheek pieces removed. Fig. 3 is a side viewof one of the terminals with the washers and cheek pieces that close theend of the casing and lock the terminal. Fig. 4 is a view looking towardthe inner end of the terminal. Fig. 5 is a view lookin toward the outerend of the ig. 6 is a side view of the terminal. Fig. 7 shows the cheekpieces which are utilized to lock the terminal. Fig. 8 shows a side viewof a terminal that may be used at one end of thecasing. Fig. 9 s a viewlooking toward the outer end of the latter terminal. Fig. 10 is a viewlooking toward the inner end of the modified terminal. Fig. 11 shows, onenlarged scale, a section of a portion of the casing, metal end sleeve,and ferrule, illustrating a manner of connecting these parts andproviding two long but restricted spiral paths over metal for the reliefof any internal pressure resulting from the blowing of the fuse.

The casing 1 of'the fuse is formed of a. tubular section of insulatingfiber or other suitable insulating material. At each end the casing isprovided with an interior thread, and screwed into each end is ametallic bushing 2 which has an exterior thread designed to be screwedinto the casing and an exterior thread designed to receive theinternally screw-threaded metal ferrule 3 that is screwed on the exposedend of each bushing when the structure is assembled. It is desirable tocut the threads of regular form and full depth in each piece and then togrind off the tops of the threads so as to leave a small spiral channel4 between the pieces when screwed together, as shown in ig. 11. Thispermits the parts to be screwed together very securely but provides twolong but restricted channels at each end of the casing for the relief ofgas pressure generated when the fusible link melts, and as the gases in.flowing through these channels pass over a considerable area ofrelatively cool metal which quickly absorbs the heat liberated, thegases become thoroughly chilled so that no flame will be emitted whenthe fuse blows, no matter how violent the action.

Each terminal has an exterior blade 5 for engagement with the usualcircuit terminal clip and an interior lug 6 provided with a perforation7 for the passage of the bolt 8 which with the nut 9 is employed todetachably secure the end of the fusible link 10 to the terminal.Permanently fastened on at least one of the terminals at the junction ofthe blade and lug is an oblong stirrup 11, the longer diameter of whichis substantially the same or slightly less than the inner diameter ofthe bushing into which it fits. Just outside of the stirrup the edges ofthe blade are cut away, forming notches 12. Slipped upon the blade ofthis terminal and fittin closely thereto is a packing washer 13 offlexible material, such as leather or cloth, and outside of this is ametallic washer 14, these washers being circular in outline and ofgreater diameter than the opening in the bushing. Between the packingwasher and the stirrup is a divided washer formed of two cheek pieces15. These cheek pieces are substantially semi-circular, and are cut awayso that they will fit upon the blade with their ends 16 fitting closelytogether in the notches in the edges of the terminal next to thestirrup. The two cheek pieces when put together are substantially thesame diameter as the washers, that is, when assembled they form a circlewhich is larger than the. opening in the metallic bushing that isscrewed into the end of the casin Projecting inward from each of thesechee pieces is a stud 17 that is designed, when the cheek pieces areplaced in position, to lie in a slot 18 milled in the outer edge of themetallic bushing.

When this terminal is placed in the casing the cheek pieces are slippedupon it from OK- posite sides and broughttogether with t e studsextending into the slots in the bushing. Then the packing washer andmetallic washer ar slipped up on the blade close against the cheekpieces and the ferrule is screwed up tightly against the metallicwasher. This clamps the washers and cheek pieces closely together andtightly against the end of the metallic bushing, the cheek pieces withtheir studs preventing the terminal from being rotated and the wholesecurely closing the end of the casing except for such passages as maybe left around the screw threads as previously described. The ferrulefits upon the metal bushing so there is no danger of crossing orbreaking the threads when it is screwed on for originally assembling orafter renewal of the fuse, and as the ferrule is screwed upon the metalbushing and the washers and cheek pieces are held between the end of themetal bushing and the metal flange of the ferrule, a very strong, firmcontact is made. The cheek pieces lock the terminal against movement inand out and hold itagainst rotation, and the stirrup acts as a baflieplate and prevents gas from blowinglup around the faces of the bladesbeing pressed tightly thereon.

Such a terminal as has been described may be used at each end of thefuse, but if desired for the purpose of simplifying the construction andprocess of assembling, the terminal may be provided with a single fixedwasher 19 provided with studs 20 adapted to enter the slots 18 in the ede of the bushing, as shown on the left in ig. 1. In this case theterminal is held securely in positioned by screwing the ferrule upon themetal bushing so that the flange of the ferrule forces the washertightly against the end of the bushing.

With the parts assembled in this manner the ferrules are easily removedafter repeated blowings of the fuse, as the engaging threads of theremovable parts are metal, and on account of this they can be made tofit tighter and can be stronger than if one thread was in theinsulation, and passages for the relief of the internal pressure areprovided, without danger of the ferrules becoming set on the ends of thecasing so as to result in damageto the structure when it is desired todisassemblethe parts for renewing the fusible link.

The invention claimed is:

1. An inclosed fuse having an insulating casing, a metallic bushingscrewed into the end of the casing, a conducting terminal plateextending into the bushing, a divided washer and an imperforate washerboth fitted on the terminal outside of end of the and compressing thewashers between the end of the bushing and the ferrule.

2. An inclosed fuse having an insulating casing, a metallic bushingscrewed into one end of the casing, a conducting terminal plate withnotched edges extending into said bushing, said notches in the terminalplate being outside of the end of the bushing, semi-circular cheekpieces fitting the notched portion of the terminal outside of andclosing the outer end of said bushing, a washer movably fitted on theterminal outside of the cheek pieces, and a ferrule screwed on thebushing against said washer.

3. An inclosed fuse having an insulating casing, a metallic bushingscrewed into one end of the casing, a conducting terminal plate withnotched edges extending into said bushing, said notches in the terminalplate being outside of the end of the bushing, a stirrup fixed on theterminal inside of the notches therein, said stirrup being wider thanthe thickness of the terminal and as long as the inner diameter of thebushing, semi-circular cheek pieces fitting the notched portion of theterminal outside of the stirrup and end of the bushing and closing theouter end of said bushing, a washer movably fitted on the terminaloutside of the cheek pieces, and a ferrule screwed on the bushingagainst said washer.

4. An inclosed fuse having an insulating casing, a metallic bushing withslots in its outer edge screwed into one end of the casing, a conductingterminal plate with notched edges extending into sald bushing, saidnotches in the terminal plate being outside of the end of the bushing,semi-circular cheek pieces fitting the notched portion of the terminaloutside of and closing the outer end of said bushing, means projectingfrom the cheek pieces into the slots in the edge of the bushing, awasher movably fitted on the terminal outside of the cheek pieces, and aferrule screwed on the bushing against said washer.

5. An inclosed fuse having an insulating casing, a metallic bushingscrewed into the end of the casing, a conducting terminal plate withnotched edges extending into the bushing, said notches in the terminalplate being outside of the end of the bushing, two semi-circular cheekpieces embracing the notched portion of the terminal outside of andclosing the outer end of said bushing, a washer movably fitted on theterminal outside the cheek pieces, said washer being circular and largerin diameter than the opening through the bushing. and a ferrule screwedupon the exterior of the bushing and compressing the washer against thecheek pieces.

6. An inclosed fuse having an insulating casing, a metallic bushingscrewed into the end of the casing, a conducting terminal plateextending into the bushing, a baffle plate fixed tightly upon saidterminal plate inside of the bushing, said bafile plate being as long asthe inner diameter of the bushing and having its outer face flush withthe end of the bushing, a divided transversely removable locking washerengaged with the terminal plate out-- side of the end of the bushing andhaving its 'oints with the terminal covered by the bafile plate, animperforate longitudinally removable washer fitted on the terminaloutside the divided washer, said washers being circular and larger indiameter than the opening through the bushing. and a ferrule screwedupon the exterior of the bushing and compressing the washers between theend of the bushing and the ferrule.

ROBERT C. COLE.

